Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $84.96   11.792%   $94.9785   $94.98   $95.00   $95.00  
  Purchase #2 $111.28   10.719%   $123.2081   $123.21   $123.20   $123.20  
  Purchase #3 $214.69   8.333%   $232.5801   $232.58   $232.60   $232.60  
  Purchase #4 $198.26   10.242%   $218.5658   $218.57   $218.55   $218.60  
  Purchase #5 $5.71   4.785%   $5.9832   $5.98   $6.00   $6.00  
  Purchase #6 $65.59   12.524%   $73.8045   $73.80   $73.80   $73.80  
  Purchase #7 $19.74   7.477%   $21.216   $21.22   $21.20   $21.20  
  7 purchase totals = $700.23       $770.3362   $770.34   $770.35   $770.40